This invention relates to apparatus for reducing the aerodynamic drag of a moving vehicle and more particularly to apparatus for reducing the air drag on trucks, trailer trucks and other similar vehicles which present a substantially broad aerodynamically resistant surface in the direction of travel of the vehicle.
In the case of trucks, trailers and other similar vehicles, the optimum useful space within the load bearing portion of the vehicle is achieved when the body of the vehicle is substantially rectangular or box-like in shape. When utilizing such a shape, however, the forward face or surface of the vehicle presents an aerodynamically resistant surface which results in a high aerodynamic drag when the vehicle is moving, particularly at speeds in excess of 50 mph. The aerodynamic resistance of the vehicle results in increased operating costs and can substantially reduce the handling characteristics of the vehicle particularly in quartering winds and crosswinds. Modifying the forward face of the cargo portion of the vehicle, such as in "round nose trailers," has been notably unaccepted by the trucking industry because of the reduction in useful cargo space.
Various prior art devices have been suggested which are adapted to be carried either by the trailing element or cargo body of the vehicle or for mounting on the cab of the vehicle for deflecting impinging air around the cargo body to reduce the aerodynamic drag. Thus, for example, Saunders in U.S. Pat. No. 3,241,876 suggests the placing of a baffle on the cab of the vehicle which deflects air upwardly over the cargo holding portion of the vehicle. Such apparatus requires reinforcement of the cab roof and is substantially of no help in improving the handling characteristics of the vehicle in crosswind. U.S. Pat. No. 697,120, also Saunders, discloses a device which is utilized in the gap between a tractor and trailer to reduce crosswind drag. This device may be utilized in combination with the air deflection baffle disclosed in U.S. Pat. No. 3,241,876 to reduce the air resistance of the vehicle in both head winds and crosswinds.
Kerrigan in U.S. Pat. No. 3,415,566 proposes a rectangularly shaped, open receptacle which is carried on the front wall of the cargo body and which traps air to produce an air buffer for diverting impinging air around the vehicular body. This device is of substantially no value in a crosswind.
Other drag reducing apparatus employed in the prior art includes the provision of air vanes or fins around the edges of the cargo carrying portion of the vehicle to deflect the impinging air stream. Operating on a different principle is a device disclosed by Dempsey in U.S. Pat. No. 2,514,695 which comprises a substantially larger blister carried on the forward face of a trailer and which blister is provided with an opening for collecting impinging air, and conduit means extending along the trailer and exiting at the rear portion of the trailer for conducting the collected air. This device requires a substantial modification of the trailer.
De Vaughn, U.S. Pat. No. 3425,740 also discloses a contoured blister which is designed to be carried on the forward face of a house trailer and which is movable between an extended awning position and a traveling position. The design of the DeVaughn device presents a substantial overhang from the front of the trailer which is unacceptable for commercial vehicles.
Other prior art devices include means for enclosing the gap between the tractor and trailer of an articulated cargo carrying vehicle to reduce the resistance of the combination. Such devices restrict vehicular operation, particularly the turning radius, and are unacceptable for commercial vehicles.
The prior art devices, although successful in varying degrees in reducing the aerodynamic resistance of a vehicle, are deficient to the extent that either substantial modifications of the vehicle are required in order to employ the devices, or it is necessary to use several devices in combination in order to achieve reduction of aerodynamic resistance in both a head flow and cross flow of air with respect to the vehicle, thereby substantially increasing the cost of air resistance reduction. The present invention represents an improvement over the prior art in that apparatus is provided for mounting on the forward face of the trailing element of a vehicle which reduces the aerodynamic resistance of the vehicle both in a cross flow and head flow situation. The apparatus of the present invention requires substantially no modification of the vehicle and is acceptable for use on commercial vehicles.